1. Field of the Invention
This invention relates generally to lithography and more particularly to a method and apparatus for increasing the selectivity of a silicon containing photoresist layer to improve profile control of etched features without decreasing wafer throughput.
2. Description of the Related Art
The ability to work selectively on small well defined areas of a substrate is paramount in the manufacture of semiconductor devices. In the continuing quest to achieve higher levels of performance and higher functional density of the semiconductor devices, the microelectronics industry is committed to applying new processes to further reduce the minimum feature sizes of the semiconductor devices.
As the feature sizes are reduced, the devices can become smaller or remain the same size but become more densely packed. As such, advances in lithographic technologies used to pattern the semiconductor devices must keep pace with the progress to reduce feature sizes, in order to allow for smaller and more dense. For example, one of the main ways to reduce the device critical dimensions (CD) through lithographic technologies has been to continually reduce the wavelength of the radiation used to expose the photoresist.
Sharp lithographic transmission becomes more of a challenge as wafers progress to higher density chips with shrinking geometries. Furthermore, as metallization transitions to dual damascene processes, lithography techniques to pattern holes or trenches in the dielectric become more critical. In particular, the photoresists employed in the lithographic techniques must provide for proper selectivity so that downstream etching processes yield sharp profiles.
Photoresists are typically polymeric materials consisting of multi-component formulations. Additionally, a photoresist may be applied as a single layer or as multiple layers where one of the layers contains silicon. Multi-layered photoresists tend to offer superior formation of a pattern, therefore, the multi-layered photoresists are desirable as semiconductor devices become smaller. However, resist compositions containing silicon have either failed to deliver adequate improvement in etch resistance or have had poor processing performance due to the unacceptable selectivity past the silicon containing layer.
As a result, there is a need to solve the problems of the prior art to improve the selectivity past the developed photoresist layer containing silicon, without simultaneously decreasing wafer throughput, so that during etching there is improved ability to distinguish between silicon containing photoresists and non silicon containing photoresists or the dielectric.
Broadly speaking, the present invention fills these needs by providing a photoresist layer that has been hardened to increase the selectivity of the hardened photoresist layer relative to an underlying photoresist or underlying dielectric. In addition, the hardening process may take place in an etch chamber so that the fabrication, e.g., etching steps, may be combined with treating processes to improve wafer throughput. It should be appreciated that the present invention can be implemented in numerous ways, including as an apparatus, a system, a device, or a method. Several inventive embodiments of the present invention are described below.
In one embodiment, an apparatus for exposing a photoresist-developed substrate is provided. In this embodiment, a chamber is included where the chamber has at least one gas inlet adapted to introduce a gas into the chamber. Also included is a support within the chamber. A substrate on the support where the substrate has at least one developed photoresist layer is included. The substrate is exposed to a curing environment within the chamber where the curing environment is defined through the introduction of the gas through the gas inlet and causing at least a portion of the developed photoresist layer to convert to a hardened layer.
In another embodiment of the invention an apparatus for curing a photoresist is provided. In this embodiment, a chamber having at least one gas inlet adapted for introducing a gas into the chamber and a support within the chamber are included. A substrate on the support where the substrate has a first photoresist layer and a second photoresist layer is included. The first photoresist layer is formulated to contain a hardening agent where the hardening agent interacts with the gas to form a hardened layer from a top region of the first photoresist layer.
In yet another embodiment of the invention, a method for increasing a selectivity of a photoresist is provided. The method initiates with providing a substrate with a developed photoresist layer, the developed photoresist layer being formulated to contain a hardening agent. Next, the substrate is exposed to a gas, where the gas is formulated to interact with the hardening agent. Finally, a portion of the developed photoresist layer is converted to a hardened layer where the hardened layer is created by an interaction of the hardening agent with the gas.
In still another embodiment of the invention, a method for curing a photoresist is provided. The method initiates with providing a substrate with a first photoresist layer and a second photoresist layer. The first photoresist layer is developed and disposed over the second photoresist layer and the first photoresist layer is formulated to contain a hardening agent. Next, the first photoresist layer is exposed to a curing environment where the curing environment includes a gas for interacting with the hardening agent. The method terminates after converting a portion of the first photoresist layer to a hardened layer where the hardened layer is configured to increase a selectivity ratio.
In still yet another embodiment a method for curing a photoresist disposed on a wafer within an etch chamber is provided. The method initiates with the introduction of a gas into the chamber through a process gas inlet, where the gas in the etch chamber defines a curing environment. Next, a wafer having a developed photoresist is exposed to the curing environment. Here, the photoresist is formulated so as to contain a hardening agent. Then, the hardening agent interacts with the curing environment, thereby converting a portion of the developed photoresist layer to a hardened layer.
The advantages of the present invention are numerous. Most notably, the formation of the hardened layer increases the selectivity ratio of the underlying photoresist layer or interlayer dielectric relative to the hardened layer of the top photoresist layer. Accordingly, any etch processes performed on the substrate with the hardened layer will etch through the underlying photoresist layer or interlayer dielectric at an increased rate relative to the etch rate of the hardened layer. Furthermore, the etch profile control will be improved as a result of the increased selectivity, thereby allowing for more accurate etch profiles as semiconductor device features continue to shrink. Additionally, an etch chamber may be utilized for curing the hardened layer. As a result, after the curing process, the substrate may be etched in the same chamber. Hence, throughput is increased and handling of the substrate is minimized.
Other aspects and advantages of the invention will become apparent from the following detailed description, taken in conjunction with the accompanying drawings, illustrating by way of example the principles of the invention.